The purpose of this study is to correlate the structural properties of the tissues of the spine with the material properties and geometrical distribution of the tissues of which these elements are composed and with age and state of degeneration. In particular, viscoelastic and rate dependent properties will be measured. Creep, relaxation, cyclic loading, and programmed variable rate tests will be performed in tension, bending, torsion, compression, and combined loading. The deformation of various key tissues, i.e., spinal cord, nerve roots and discs during structural tests of intact spinal segments obtained at autopsy will be determined. To aid in the interpretation of creep test results a series of mechano-chemo-experiments is being developed. These experiments will be creep tests of intact motor units with a controlled external chemical environment. A miniature pressure transducer will be inserted in the nucleus pulposus to monitor the pressure. This experiment will be performed with various external chemical environments to study the mechanisms of creep recovery observed in the intervertebral disc. The long-range goal of this research is to provide currently unavailable information regarding structural and viscoelastic properties of the tissues of the spine to provide a quantitative framework for the development of mechanisms of lower back disorders and pain.